Mammography is a common procedure used to screen women for
breast cancer.

3D mammography combined with 2D mammography or synthetic 2D
mammography can detect more cases of breast cancer as compared to 2D
mammography alone.

The flipside is that the combined procedure is also associated
with a risk of picking up more false-positive breast cancer cases, thereby
causing excess stress for the wrongly-diagnosed woman.

A combination of 3D mammography with 2D or synthetic 2D mammography can detect more cases of breast cancer as compared to 2D mammography alone. However, the combined procedure also increases the risk of over-diagnosing breast cancer. A recent study comparing these mammography procedures has been published in The Lancet Oncology.

Breast cancer is the second biggest cause of death in women all over the world. Mammography has been used for the screening of breast cancer to detect it in the early stages before it produces any symptoms and when it can be completely cured. The survival rate is almost over 93% in the first five years in the case of patients whose breast cancer is detected at an early stage. During the test, the breast tissue is compressed between two plates and images are taken.

‘The mammography procedure used to screen breast cancer should be based on its sensitivity in detecting cancer as well as the risks of over-diagnosing cancer.’

Conventional mammography produces images on films. Digital mammography now permits obtaining a digital version of the image on a computer, which can be enhanced or magnified to make the picture clearer and the diagnosis more accurate. It also permits sending the file electronically from one medical center to another. Digital images also appear to produce more accurate images in young women with dense breasts as dense breasts and cancer appear white in color and make it difficult for the clinician to differentiate between the two.

A mammogram usually produces 2 dimensional (2D) images of the breast. 3D mammography, also called tomosynthesis, is also available. In contrast to 2D mammography, 3D mammography creates thin slices of the breast similar to a CT scan to produce a pseudo-3D image of the breast. It is performed at the same time as a 2D mammogram, resulting in a slightly higher radiation exposure as it takes approximately 30 seconds more to capture the image in 3D. To avoid this excess radiation, instead of combining the 3D and 2D mammography, only 3D mammography can be done and synthetic 2D images may be reconstructed from the images obtained from the 3D mammography. 3D mammography was approved as an imaging modality by the FDA (Food and Drug Administration) in the year 2011.

Researchers from The Screening with Tomosynthesis Or standard
Mammography-2 (STORM-2) study in Italy compared the breast cancer cases
detected using 2D mammography alone, or 3D mammography in combination with 2D
mammography or synthetic 2D mammography. The study was conducted in 9672 women aged
49 years or more over a period of 2 years. Screening detected the presence of breast cancer in 85 patients, which included 74 invasive breast cancers.

The researchers found that the combined procedures detected a larger number of breast cancer cases as compared to the 2D mammograms alone. Cancer detection rate was 8.5 per 1000 screens for 2D-3D mammography and 8.8 per 1000 screens for 2D synthetic-3D mammography while it was 6.3 per 1000 screens in the case of 2D mammography alone. There was no significant difference in the detection of breast cancer cases between the combined procedures (3D-2D mammography versus 3D-synthetic 2D mammography). Thus, the combined procedures appeared to perform better in screening women for breast cancer.

This prospective population-based
screening study was preceded by STORM study in 2013 which investigated the
effect of combining 2D and 3D mammography for screening breast cancer.

There was also a flipside to the
study. The combined procedures detected a significant number of false-positive
breast cancers - that is, they detected more cancers in women who did not
actually have them, as compared to the 2D procedure. Such false positive
results could cause unnecessary stress to the misdiagnosed woman and result in
further tests conducted, thereby increasing the overall cost of diagnosing a
condition that does not exist.

Therefore, the results need to be
interpreted in terms of the benefits of increased rates of detection of breast
cancer and the risk of overdiagnosis.

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